Book spelling and grammar corrections (#3659)

## Issue Addressed

There are few spelling and grammar errors in the book.

## Proposed Changes

Corrected those spelling and grammar errors in the below files
- book/src/advanced-release-candidates.md
- book/src/advanced_networking.md
- book/src/builders.md
- book/src/key-management.md
- book/src/merge-migration.md
- book/src/wallet-create.md


Co-authored-by: Kausik Das <kausik007007@gmail.com>
Co-authored-by: Kausik Das ✪ <kausik007007@gmail.com>

CONTRIBUTING.md

@@ -46,7 +46,7 @@ questions.
    (github.com/YOUR_NAME/lighthouse) of the main repository
    (github.com/sigp/lighthouse).
 3. Once you feel you have addressed the issue, **create a pull-request** to merge
-   your changes in to the main repository.
+   your changes into the main repository.
 4. Wait for the repository maintainers to **review your changes** to ensure the
    issue is addressed satisfactorily. Optionally, mention your PR on
 [discord](https://discord.gg/cyAszAh).

book/src/advanced_networking.md

@@ -59,7 +59,7 @@ TCP and UDP ports (9000 by default).
 Lighthouse has a number of CLI parameters for constructing and modifying the
 local Ethereum Node Record (ENR). Examples are `--enr-address`,
 `--enr-udp-port`, `--enr-tcp-port` and `--disable-enr-auto-update`. These
-settings allow you construct your initial ENR. Their primary intention is for
+settings allow you to construct your initial ENR. Their primary intention is for
 setting up boot-like nodes and having a contactable ENR on boot. On normal
 operation of a Lighthouse node, none of these flags need to be set. Setting
 these flags incorrectly can lead to your node being incorrectly added to the

book/src/builders.md

@@ -188,7 +188,7 @@ with the builder network:
 INFO Published validator registrations to the builder network
 ```
 
-When you succesfully propose a block using a builder, you will see this log on the beacon node:
+When you successfully propose a block using a builder, you will see this log on the beacon node:
 
 ```
 INFO Successfully published a block to the builder network

book/src/key-management.md

@@ -103,7 +103,7 @@ opt-in). Instead, we assert that since the withdrawal keys can be regenerated
 from a mnemonic, having them lying around on the file-system only presents risk
 and complexity.
 
-At the time or writing, we do not expose the commands to regenerate keys from
+At the time of writing, we do not expose the commands to regenerate keys from
 mnemonics. However, key regeneration is tested on the public Lighthouse
 repository and will be exposed prior to mainnet launch.
 

book/src/merge-migration.md

@@ -2,7 +2,7 @@
 
 This document provides detail for users who want to run a merge-ready Lighthouse node.
 
-> The merge is occuring on mainnet in September. You _must_ have a merge-ready setup by September 6
+> The merge is occurring on mainnet in September. You _must_ have a merge-ready setup by September 6
 > 2022.
 
 ## Necessary Configuration

book/src/wallet-create.md

@@ -11,7 +11,7 @@ backed up, all validator keys can be trivially re-generated.
 
 The 24-word string is randomly generated during wallet creation and printed out
 to the terminal. It's important to **make one or more backups of the mnemonic**
-to ensure your ETH is not lost in the case of data loss. It very important to
+to ensure your ETH is not lost in the case of data loss. It is very important to
 **keep your mnemonic private** as it represents the ultimate control of your
 ETH.